Frequently Asked Questions

QUV Weathering Tester

Q: Can the results of tests in two different conditions be compared?

Background:  For a test in QUV we can choose between two conditions that give the same amount of total energy: 

Test A: Irradiance 0.65W/m2 for a time of 3000h.
Test B: Irradiance 0.83W/m2 for 2500h.

The testing samples are films, with a thickness between 80 and 100 micron.  At the end of the each test, we verify the change of color in grey scale and the mechanical property retain.

Can we compare the two results?


Answer: It is common to assume that the two exposures are the same, but in many cases the two would yield different results. There are complex synergies between irradiance, heat, and moisture. Generally, when this question is studied, there is a much bigger difference between irradiance setpoints. The question is something like this: if you double the irradiance of the exposure, can you cut the test time in half and achieve the same results?

Sometimes there is a linear relationship between irradiance and speed of degradation, but sometimes not. In the example in the question, the difference is small, so there is greater likelihood that the results are comparable.

Still, I would conduct your own study and find out. I would be interested in learning of your results.

Q: What is the difference between QFS-40 and UVB-313EL Lamps?

QFS-40 and UVB-313EL lamps are both used in QUV accelerated weathering testers to provide fluorescent UV light that includes a significant UVB component for faster testing. The diagram below shows that both have similarly-shaped spectral power distributions. How do these lamps differ, and which one is best for use in your QUV?

Spectral power diagram

The QFS-40 lamp was developed to meet the specifications of SAE J2020, which, when written, had a hardware-specific requirement to use this lamp. That hardware-specific requirement has been removed in SAE J2020 and in most standards that are based on SAE J2020.

UVB-313EL lamps were developed later, and operate with the QUV’s SOLAR EYE irradiance control system to provide a more consistent and repeatable level of irradiance than using QFS-40 lamps in a QUV/basic, due to lamp aging, maintenance, and environmental conditions. UVB-313EL lamps are significantly less expensive than QFS40 lamps because far greater volumes of UBV-313EL are manufactured.

If your QUV has SOLAR EYE irradiance control, you should use UVB-313EL lamps and set the irradiance to 0.48 W/m2 at 310 nm for SAE J2020 and standards based on it, even if those standards have not been updated to include the UVB-313 lamp. This is the most cost-effective and best-performing option when irradiance control is available.

If your QUV does not have irradiance control (QUV/basic or old style models), you should continue to use QFS-40 lamps to maintain comparable irradiance levels to what is intended by a test standard or historical practice. UVB‑313EL lamps used in QUV testers without irradiance control will generate irradiance that is significantly higher than QFS-40 lamps in the same tester.

 

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